Monitoring standing herbage on granitic soils in the Big Horn Mountains, Wyoming, USA

Abstract

Monitoring annual herbage use in rangelands is desirable for scientific management but problematic due to the difficulty and expense of making direct measurements of sufficient precision. We used a Robel pole with 1.27 cm alternating white and gray bands to indirectly measure standing herbage. This technique enables a smooth transition in the basis of annual use monitoring from percent use to residual herbage and overcomes the difficulties alluded to above. Our study was conducted in the southern Bighorn National Forest, Wyoming on granitic soils and within the Idaho fescue (Festuca idahoensis Elmer) vegetation type. The objectives were to develop and validate the relationship between Robel pole visual obstruction readings and clipped standing herbage, and develop guidelines for monitoring and estimation of optimum sample size. Clipped standing herbage ranged from 134 to 3792 kg dry matter (DM) ha−1 with a mean of 1558 kg DM ha−1. Visually obstructed bands (band = 1.27 cm) averaged 6.1 and ranged from 0.2 to 19.5. Approximately 75% of the variation in standing herbage was explained by linear regression on visual obstruction measurements. Both intercept and slope of the regression were highly significant (P = 0.001). The standard error of the estimate for a single observation was 458 kg DM ha−1. Cluster analyses grouped the visual obstruction readings into four management categories. This monitoring tool provides pertinent information for managers to develop guidelines based on band and/or standing herbage for natural areas, wildlife and livestock use.

Monitoring mid‐grass prairie in southwestern South Dakota and northwestern Nebraska, USA

“…For example, if a VOR of band 6 warrants the desired removal of livestock, then the one‐sided Student's t ‐test (α = 0.05) is appropriate to test for differences less than the established guideline of band 6 (Steel and Torrie ; Uresk and Benzon ; Uresk et al . ). At the landscape level, monitoring efficiency is related to size of the land base (figure 5 in Benkobi et al .…”

“…(), Uresk and Benzon (), and Uresk et al . (). A modified 2.54‐cm diameter Robel pole was painted with alternating 1.27‐cm white and gray bands.…”

“…Grasslands were sampled from early July near peak standing herbage, to early October on ungrazed to heavily grazed pastures. All procedures and methods followed Robel et al (1970), Uresk and Benzon (2007), and Uresk et al (2010). A modified 2.54-cm diameter Robel pole was painted with alternating 1.27-cm white and gray bands.…”

“…; Uresk and Benzon ; Uresk et al . ). The use of the Robel pole for monitoring has received considerable attention in the published work (Robel et al .…”

“…Monitoring annual herbage use on rangelands by direct clipping measurements is problematic due to the difficulty and expense of obtaining an adequate sample size of sufficient precision. To meet the increasing demand for intensive monitoring of vegetation for livestock grazing and wildlife habitat on public rangelands, the modified Robel pole is an improved, accurate and cost-effective methodology (Benkobi et al 2000;Uresk and Benzon 2007;Uresk et al 2010). The use of the Robel pole for monitoring has received considerable attention in the published work (Robel et al 1970;Volesky et al 1999;Vermeire and Gillen 2001;Higgins et al 2005).…”